1. Field of the Invention
The invention concerns a hydrostatic travelling mechanism for track-laying vehicles, in which at least one motor adjustable in working volume is assigned to the tracks and to which at least one pressure medium delivery line connected to a hydrostatic pump leads and which has a working volume adjusting device that can be influenced by a signal dependent on the operating pressures, where the drive motors can be supplied with different quantities of pressure medium independently of each other.
2. Description of the Art
Such drive mechanisms are used, for example, as crawler drives in construction machinery. A hydrostatic drive unit with its own drive motor is usually assigned to each of the two track laying mechanisms. The travel motor can have a constant absorption volume or can be a variable displacement or regulating motor. With an identical transmission to both hydrostatic drive units the vehicle moves straight ahead. Different amounts of oil are delivered to the drive motors for cornering; this occurs in hydrostatic drive units in closed circuit by a different adjustment of the working volume of the adjusting pump assigned to each drive unit. In hydrostatic drive units in open circuit one or more variable displacement or regulating pumps supply the two drive units. The allocation of different oil quantities for the two drive units then takes place through multiway-acting valves. A speed change in the track-laying vehicle is effected by identical regulation of the two travel motors in both cornering and straight-forward travel. The working volume regulation of the travel motors can be effected by adjusting the operating pressure of the hydrostatic drive unit. Above a certain operating pressure, there is a transition from minimal to maximum absorption volume in the travel motor, by which the speed is decreased and the torque increased.
When vehicles equipped with such travelling gears are moved on rough ground, variable travel resistances usually arise at the two track-laying mechanisms or at the tracks. For example, if one of the tracks has to surmount an obstacle, its travel resistance increases and thus also the operating pressure in the assigned hydrostatic drive unit. This induces a working volume regulation of the travel motor of this drive unit and thus a transmission change in the direction toward a lower speed. The speed ratio of the two tracks is thus modified and the vehicle begins to move in a direction that is undesirable, which requires a corrective intervention by the driver. This is the case in both straight-forward travel of the vehicle and in cornering, by which such a vehicle is practically uncontrollable with regard to steerability.